1. Field of the Invention
The present invention relates to a picture recording apparatus, and more particularly, but not exclusively, to CRT illumination of silver halide negatives for printing color pictures on photographic print paper, or other photographic media.
2. Description of the Prior Art
There has been generally known a device for illuminating color photographic negatives in order to produce hard copies referred to in the art as a lamphouse. The purpose of a lamphouse is to illuminate the negative in a controlled fashion so as to expose the color photographic print paper's three dye layers to faithfully reproduce the image captured on the negative.
The term lamphouse is further subdivided into four categories according to their method of operation. The methods have been described in the art as white light, additive, subtractive, and false color.
The white light method employs a single or plurality of incandescent lamps whose radiation path is partially or fully interrupted by a plurality of color optical filters. All of the filters remain stationary throughout a batch operation, the negatives in the batch do not vary widely in transmission density or color balance.
The additive method employs a single or plurality of incandescent lamps whose radiation path is partially or fully interrupted by a plurality of color optical filters; however, the negative is illuminated by each of the colors sequentially, red, blue and green. The time of illumination may vary from color to color. In another additive method known to the art, illumination by color is simultaneous and the time of illumination is constant; however, the level of luminance may vary. The filters may or may not be stationary. This method is used where negative densities and color balance vary widely.
The subtractive method employs a single or plurality of incandescent lamps whose radiation path is partially or fully interrupted by a plurality of color optical filters, initially the negative is illuminated by all colors; red, blue and green simultaneously. However, when the individual dye layer exposure of the photographic paper has been satisfied, the filter associated with that dye layer is mechanically introduced into the radiation path to cut off the associated portion of the radiation spectrum. This method is used where negative densities and color balance vary widely.
All of the methods and apparatus for illuminating negatives mentioned above have these common characteristics: they all employ incandescent lamps, they all require radiation separators of one form or another, and they all require blowers to remove convected heat from the device.
Furthermore, all of the above mentioned apparatus and or methods require a device known in the art as a filter pack to manipulate the Kelvin temperature of the radiated output of the incandescent lamps to a workable center range, in addition to individual color optical filters, cyan, yellow and magenta for the subtractive method, and red, blue and green for the additive method. The individual filters are required to compensate for deviations from workable center. Prior art also requires the use of a device known to the art as a capping or dark shutter to interrupt the radiated output of the incandescent lamp or lamps to control the exposure period of the photographic paper.
Halogen incandescent lamps depend on incandescence or the heat produced by electrical currents through their filaments to produce radiation in the visible light spectrum, and at best are only 26 percent efficient in the production of radiation in the visible light spectrum. The mass of the filaments in incandescent lamps has an inertia to heating and cooling; and therefore, cannot be operated on and off with the rapidity required by high production capacity photoprinting apparatus. Further, the type of halogen incandescent lamps employed in prior art have a life expectancy of approximately 40 hours when operated at rated voltages. Halogen incandescent lamps emit a broad and continuous spectrum of radiated energy in the visible light region, in addition to ultra violet and infrared radiation; and therefore, must employ filters to control the photographic process. In all of the above described methods and apparatus, the hard copy media is coated with a plurality of layers of silver halide compounds known to the art as photosensitive dye layers.
In another version of prior art, the hard copy media is a paper substrate whose photosensitive surface is impregnated with a plurality of plastic microbeads containing dyes of cyan, magenta and yellow. When exposed to radiation in the ultraviolet spectrum and near ultraviolet regions of the visible light spectrum, the microbeads will harden. The beads containing yellow dye are sensitive to blue light, while the beads containing magenta and cyan dyes are sensitive to select regions of the ultraviolet radiation spectrum. After exposure, the paper is passed between pressure rollers, where the hardened beads are crushed, spilling their dyes into the paper fibers, thus reproducing the color image captured on the negative, each microbead representing a color pixel.
Because color photographic negatives only filter light in the visible light spectrum, a plurality of color separation internegatives must be prepared in order to filter radiation and expose the hard copy in the ultraviolet spectrum. The internegatives are then interposed between the hard copy and a source of ultraviolet light, such as carbon arcs and/or mercury vapor lamps. Exposures are time consuming because they are sequential and require positive registration of the plurality of negatives. This method is known in the art as the false color method.
It is therefore an object of the present invention to provide a method of and apparatus for illuminating photographic negatives to produce a hard copy without the use of filter packs, individual color optical filters, dark or capping shutters and incandescent lamps. It is a further object of the present invention to render the printing of color photographic paper from color photographic negatives completely automatic without human intervention.